This invention relates to wedges for use with ties in maintaining a predetermined spaced relation between opposed forms prior to and during the pouring of a concrete wall in the space between the forms. The invention is particularly concerned with wedges for use with form ties which are designed to have their outer end portions broken off inside the wall after the concrete has set and the forms have been removed.
In one conventional use of such ties, they may have a shoulder or other spacer adjacent to each end thereof which butts the inner surface of a form. The end portion of the tie beyond this spacer passes through a hole in the form and has a head on its outermost end which cooperates with clamping means and reinforcing lumber ("forms") to brace the assembled formwork against the internal hydraulic pressure developed while the fluid concrete fills the space between the forms.
The co-owned Edgar et al U.S. Pat. No. 5,050,365 of 1991 describes a problem affecting the utility of such ties of the then conventional construction arising from the fact that during erection of the forms and their supporting lumber, the mechanical connection between the head of each tie and an adjacent wale is provided by a wedge designed to apply tension to the end portion of each tie between each head and the spacer which engages the inner face of the adjacent form.
That problem was that with conventional ties and associated wedges, instead of maintaining essentially axially directed tension on the end portions of each rod, forces were developed which caused twisting of one or both of the rod heads where they interconnected with the remainder of the rod. These twisting forces were sometimes so severe as to cause the head of the rod to snap off and thus render the rod inoperative for the purpose for which it was intended.
In accordance with the Edgar patent, the problem and effect on conventional ties as outlined above were eliminated by a novel construction of each tie wherein a portion of the tie where each head interconnects with the rod is of larger cross-sectional dimensions than the remainder of the rod, although less than those of the head. The resulting reinforcement of the interconnection between the head and the rod overcame any tendency to premature snapping of the rod at its junction with a head.
In the use of the ties of the Edgar patent, however, it was found that the new ties so successfully resisted the forces previously causing conventional ties to break prematurely that the effect of those forces was transferred to the wedges of conventional construction. For example, wedges of the configuration shown in the above Edgar patent which were formed of sheet steel of an accepted thickness tended to buckle or collapse.
More specifically, the conventional wedge was formed of sheet metal of uniform thickness with an elongated slot through which the head and adjacent portion of a rod projected, and the tensioning force of the wedge was applied to the rod by engagement between the sloping sides of the slot and the axially inner end of the rod head. The problem was that the portion of the wedge along each side of the slot would tend to collapse, usually sequentially rather than simultaneously, but either way, the result was to lose the tension on the rod and thus permit undesired outward bowing of the adjacent portion of the form while the concrete wall was being poured or had not yet set beyond an essentially fluid condition.